Stair climbing has become recognized as a particularly effective type of aerobic exercise and as a result, exercise machines facilitating this type of exercise are becoming increasingly popular for both home and health club use.
There have been a wide variety of approaches taken in designing stair climbing apparatus including the simulation of an actual stair case as illustrated in U.S. Pat. Nos. 3,497,215 and 4,687,195. Another popular approach has been to simulate the action of stair climbing by using a pair of reciprocating pedals. Examples of this approach are disclosed in U.S. Pat. Nos.: Des. 263,490, 3,316,819, 3,529,474, 3,628,791, 3,979,302, 4,496,147, 4,600,187, 4,676,501, and 4,720,093.
In U.S. Pat. No. 4,708,338, a stair climbing apparatus is disclosed where two pedals operate independently of each other and are connected to a force generating alternator through a speed increasing transmission that, in turn, is connected to the pedals by a pair of chains running over a pair of one way drive pulleys. A microprocessor is used to control the alternator so that a variety of exercise programs can be implemented.
In addition to stair climbing apparatus where two pedals operate independently of each other, a reciprocating type stair climbing apparatus disclosed in U.S. patent application Ser. No. 07/426,909 filed on Oct. 29, 1989 and assigned to the assignee of the present application discloses an apparatus where the two pedals are directly connected to each other, thereby allowing the range of pedal motion to be measured. The two pedals in the stair climbing apparatus disclosed in U.S. patent application Ser. No. 07/426,909 are connected by a drive chain which is also connected via a speed increasing transmission to a resistance force generating alternator. Speed information is transmitted to the microprocessor controlled alternator which, in turn, governs the rate at which the pedals reciprocate.
Chain driven climbing apparatus, however, tend to be noisy due to the characteristics of the drive chain. One source of the noise results from the chain running over chain sprockets in the apparatus. In addition, the inelasticity of the chain results in a certain roughness of pedal operation as the pedals reciprocate from a depressed to an elevated position and vice-versa.
Along with being noisy, drive chains are relatively expensive although chain driven stair climbing apparatus such as the apparatus disclosed in U.S. patent application Ser. No. 07/426,909 have been commercially successful. Not only are the drive chains themselves expensive, but so are the many corresponding transmission components of the stair climbing apparatus such as the sprockets which must be designed for the wear and tear caused by the heavy drive chain. These components must be of sufficient size and durability to accommodate a drive chain thereby adding to the cost of the stair climbing apparatus.
As a result it is desirable to decrease the manufacturing expense, improve the smoothness of pedal motion and decrease noise of stair climbing apparatus.